A fix is available
APAR status
Closed as program error.
Error description
Sysplex distributor is configured with VIPAROUTE. The routing table is using a route with a MTU of 8992 to reach the target systems. If the TCSR drops to 16 or below, a alternate route is looked for. The alternate route has a smaller MTU. If packets of the smaller MTU size are sent to sysplex distributor, sysplex distributor tries to forward them with GRE headers over the smaller MTU route. No ICMP fragmentation needed messages are generated if the packet is dropped by a switch or router at the interface level. Application connections will timeout because the packets will never reach the target. . VERIFICATION STEPS: 1) VIPADISTRIBUTE configured along with VIPAROUTE 2) MTU difference between routes used for VIPAROUTE and alternate route to that target 3) Netstat VDPT will show the TCSR has descresed for a port on the target 4) Netstat VCRT detail will show the interface being used on the connection is the interface with a smaller MTU 5) SYSTCPIP trace option XCF will show entry: Refresh VIPAROUTE IPv4 but the routing table hasn't changed.
Local fix
Problem summary
**************************************************************** * USERS AFFECTED: All users of the IBM Communications Server * * for z/OS Version 1 Release(s) 9, 10 and 11 * * IP and Sysplex Distributor. * **************************************************************** * PROBLEM DESCRIPTION: Connections using Sysplex Distributor * * and VIPAROUTE may timeout. * **************************************************************** * RECOMMENDATION: * **************************************************************** A VIPAROUTE is used between a Sysplex Distributor and a target using an initial Maximum Transmission Unit (MTU). The initial route may become unusable and an alternate route may be selected. However the initial MTU will still be used to send packets. If the alternate route has a smaller MTU than the initial route, then packets may be discarded along the alternate route resulting in a connection timeout. +-------------------------------------------------------------+ + Please check our Communications Server for OS/390 homepages + + for common networking tips and fixes. The URL for these + + homepages can be found in Informational APAR II11334. + +-------------------------------------------------------------+
Problem conclusion
The module EZBIPOUT has been modified to use the correct MTU of the route. * Cross Reference between External and Internal Names
Temporary fix
Comments
APAR Information
APAR number
PK87062
Reported component name
TCP/IP V3 MVS
Reported component ID
5655HAL00
Reported release
1A0
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2009-05-20
Closed date
2009-06-25
Last modified date
2009-08-03
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UK47760 UK47761 UK47762
Modules/Macros
EZBIPOUT
Fix information
Fixed component name
TCP/IP V3 MVS
Fixed component ID
5655HAL00
Applicable component levels
R1A0 PSY UK47760
UP09/07/23 P F907
R1B0 PSY UK47761
UP09/07/23 P F907
R190 PSY UK47762
UP09/07/23 P F907
Fix is available
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Document Information
Modified date:
03 August 2009